From 4ed0d3e6c64cfd9ba4ceb2099b10d1cf8ece4320 Mon Sep 17 00:00:00 2001 From: Fenghua Yu Date: Fri, 24 Apr 2009 17:30:20 -0700 Subject: Intel IOMMU Pass Through Support The patch adds kernel parameter intel_iommu=pt to set up pass through mode in context mapping entry. This disables DMAR in linux kernel; but KVM still runs on VT-d and interrupt remapping still works. In this mode, kernel uses swiotlb for DMA API functions but other VT-d functionalities are enabled for KVM. KVM always uses multi level translation page table in VT-d. By default, pass though mode is disabled in kernel. This is useful when people don't want to enable VT-d DMAR in kernel but still want to use KVM and interrupt remapping for reasons like DMAR performance concern or debug purpose. Signed-off-by: Fenghua Yu Acked-by: Weidong Han Signed-off-by: David Woodhouse --- arch/x86/include/asm/iommu.h | 1 + arch/x86/kernel/pci-dma.c | 6 ++++++ arch/x86/kernel/pci-swiotlb.c | 3 ++- 3 files changed, 9 insertions(+), 1 deletion(-) (limited to 'arch/x86') diff --git a/arch/x86/include/asm/iommu.h b/arch/x86/include/asm/iommu.h index af326a2975b5..fd6d21bbee6c 100644 --- a/arch/x86/include/asm/iommu.h +++ b/arch/x86/include/asm/iommu.h @@ -6,6 +6,7 @@ extern void no_iommu_init(void); extern struct dma_map_ops nommu_dma_ops; extern int force_iommu, no_iommu; extern int iommu_detected; +extern int iommu_pass_through; /* 10 seconds */ #define DMAR_OPERATION_TIMEOUT ((cycles_t) tsc_khz*10*1000) diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index 745579bc8256..8cad0d854242 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -160,6 +160,8 @@ again: return page_address(page); } +extern int iommu_pass_through; + /* * See for the iommu kernel parameter * documentation. @@ -209,6 +211,10 @@ static __init int iommu_setup(char *p) #ifdef CONFIG_SWIOTLB if (!strncmp(p, "soft", 4)) swiotlb = 1; + if (!strncmp(p, "pt", 2)) { + iommu_pass_through = 1; + return 1; + } #endif gart_parse_options(p); diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c index 221a3853e268..3a0c51e0ba6d 100644 --- a/arch/x86/kernel/pci-swiotlb.c +++ b/arch/x86/kernel/pci-swiotlb.c @@ -71,7 +71,8 @@ void __init pci_swiotlb_init(void) { /* don't initialize swiotlb if iommu=off (no_iommu=1) */ #ifdef CONFIG_X86_64 - if (!iommu_detected && !no_iommu && max_pfn > MAX_DMA32_PFN) + if ((!iommu_detected && !no_iommu && max_pfn > MAX_DMA32_PFN) || + iommu_pass_through) swiotlb = 1; #endif if (swiotlb_force) -- cgit v1.2.2